I've been into astronomy for a while and would like to start taking pictures of the sky. I need a camera that will do timed exposures and high resolution but I'm not looking to spend my paycheck on it. I've looked around and there are TONS of different cameras. I've 'heard' great things about the Canon SLR's But, what price should I be expecting to buy one of these things at? (used) Should I get the 40d or will the 20d work or the Rebel? If anyone has a suggestion It would greatly be appreciated. I know you guys probably get this type of thread on a daily basis. The camera will be used for astronomy 90% of the time.